Respiratory mask assemblies such as the Mirage® nasal mask assembly manufactured by RedMed Ltd. and used for treatment of SDB such as Obstructive Sleep Apnea (OSA) are typically held in position on a patient's head by a headgear assembly. A headgear assembly typically includes a pair of side portions and a rear portion. The side portions are adapted to engage with the patient's mask and the rear portion is adapted to engage the back of the patient's head.
Headgear assemblies are structured to position and stabilize a patient interface, such as a nasal mask, on a patient's face so that a good seal can be maintained. In addition, the headgear assembly should be comfortable so that a patient can wear the mask assembly at night while they sleep. Many prior art headgear assemblies are uncomfortable to wear for long periods.
For reasons of costs, it is desirable to be able to cut headgear assemblies from a flat piece of fabric or composite, yet in use the headgear assembly should conform to a complex three-dimensional shape. Hence a problem to overcome is to have a design of headgear assembly which can be easily manufactured by cutting or stamping, and yet in use be able to fit a wide range of head shapes and sizes.
A given headgear strap is typically held in position using hook and loop material, for example VELCRO®, by passing an end of the strap through a loop on the mask and then folding it back onto itself. In this way, the strap can be somewhat adjusted to suit the particular needs of the patient in order that a comfortable effective mask seal be effected.
The size and shape of a headgear assembly affect how well it fits a patient. If headgear straps are too short they cannot be used to secure a mask on a large head. If headgear straps are too long they have too much excess material when used on a small head. Similarly if the headgear assembly is the wrong shape then it will not secure the mask in position.
A problem with prior art headgear assemblies is that they do not effectively cover the broadest possible range of patients and thus there are some patients unable to find suitable standard headgear assemblies.
For example, a known headgear assembly 700, commercially sold under the name of Activa® by ResMed Ltd., is illustrated in FIGS. 1-3. Further details of this headgear assembly are disclosed in U.S. patent application Ser. No. 10/655,602, filed Sep. 5, 2003, the entirety of which is hereby incorporated herein by reference.
As illustrated in FIG. 1, the headgear 700 includes a pair of top straps 702, a pair of bottom straps 704 and a rear portion 708. The rear portion 708 is shaped generally like an isosceles triangle with the base 709 of the triangle being arc-like and associated with the top straps 702. A tab 703 with hook & loop material is secured to an end of each of the straps 702 and 704, as shown in FIGS. 1 and 2.
In the illustrated embodiment, the top straps 702 have a length of 610 mm and the bottom straps 704 have a length of 660 mm. These lengths are measured without including the tabs 703 and with the headgear 700 laid flat in an unstretched state. Having a strap of a suitable length means that there is sufficient strap to pass through the connection portion of a mask (not shown) and then fold back so that the hook and loop material on each tab 703 can find sufficient region of the headgear assembly with which to engage.
Each of the straps 702, 704 has a standard width portion 705 and a widened portion 706. In the illustrated embodiment, the height of the headgear assembly 700 is 148 mm. This height is measured from the top of the top straps 702 to the bottom of the bottom straps 704 in the standard width portion 705. Also, the headgear assembly 700 has a height of 196 mm from the bottom of the bottom strap 704 to the top 709b of the arc-like base portion 709. This height dimension contributes to ensuring that a sufficient portion of the crown of the patients head is clasped by the headgear assembly 700.
The headgear assembly 700 is structured for use with one mask embodiment, and provides dimensions (exemplified above) that may not effectively cover the broadest possible range of patients, including patients that have head dimensions that are larger than or smaller than the average patient.
While headgear assemblies can be customized to suit individuals, customized articles tend to be more expensive than mass-produced ones, in the same way that visiting a bespoke tailor might produce better fitting clothes at greater expense. Furthermore, the process of customized fitting (for example cutting up or extending a given headgear assembly) can take time. Thus, it is generally desirable to have standard headgear assembly which fit the broadest range of patients.